Method of manufacturing chilled cast iron and product thereof



Patented Apr. "28, 1942' METHOD OF MANUFACTURING CHILLED CAST IRON AND PRODUCT THEREOF Oliver Smalley,

Pittsburgh, Pa.,

assignor to Meehanite Metal Corporation, Pittsburgh, Pa.,

a corporation of Tennessee N Drawing. Application April 14, 1938,

Serial No. 202,133

9 Claims.

This invention relates to the treatment of molten cast iron in the manufacture of castings and has for its object the production of metal chilled castings characterized by extreme hardness and density.

More particularly, the invention comprehends methods of producing chilled castings and the products thereof having a hard chilled outer zone and a gray inner zone produced by introducing into molten cast iron tellurium in an amount up to 2% and casting against a metal chil The product is produced by casting the iron against a metal chill, thereby increasing both the depth and hardness of the chill over that obtainable in the absence of the tellurium and producing a sharp line of demarcation substantially free of mottling between the hard chilled outer zone and non-chilled gray inner zone of the casting.

The invention also involves the introduction into molten cast iron, in addition to tellurium, of a graphitizing agent, the amount of tellurium in relation to the graphitizing agent being suffi cient to cause the tellurium to reverse the graphitizing effect of the agent.

The invention further involves the introduction into molten cast iron, in addition to tellurium, of an agent selected from a class consisting of copper, nickel and molybdenum in an amount effective to produce increased hardness and toughness over that obtainable by tellurium alone.

A further feature of the invention is the introduction into molten cast iron, in addition to tellurium, of both a graphitizing agent and an agent selected from a class consisting of copper, nickel and molybdenum in an amount suflicient to produce increased hardness and toughness.

Other objects of the invention include products of the aforesaid methods; all as hereinafter described and claimed.

The expression white cast irons, is used to refer to irons containing more than 1.7% carbon in which the carbon is substantially all in the form of iron carbide, the said irons having a white fracture and being hard and difficult to machine.

The expression gray iron" is intended to include all irons having a gray fracture that are readily machineable with ordinary tools and which contain more than 1.7% carbon and, in most cases, an important percentage of silicon and smaller quantities of manganese, sulphur and phosphorus, not more than 1.0% carbon being in the combined form, the remainder being i present as free carbon (graphite). The expression mottled cast iron" is intended to include those irons containing more than 1.7% of carbon, with or without important quantities of silicon, in which from 34% to of the total carbon content is present in the form of iron carbide.

Added to any molten cast iron, which on casting would contain free graphite, an amount of tellurium as low as .0001% will immediately change it to a. hard white iron, similar in properties to any of the so-called hard, white ordinary or alloy cast irons. The quantity of tellurium which is added may vary, but the upper useful limit seems to be about 2.0%, and less than 1.0% is preferable.

In the case of ordinary gray cast iron which would normally give a soft free machining casting, it is preferred to make the additions in the cupola spout as it runs into the ladle, although it may be added to the ladle.

In order to illustrate the efiect of the addition of tellurium as above described, a series of castings were made with different proportions of tellurium, and the hardness of each casting was measured. The iron which was used in these tests contained, after pouring without the addition of tellurium, 2.2% of graphite, .80% of combined carbon, 1.35% of silicon, .80% of manganese, 095% of sulphur, and .15% of phosphorus and is referred to below as a standard gray iron. For the purpose of these tests, the iron, with and without the addition of tellurium, was cast in the form of a square bar 2" x 2" x 4", and, after cooling, it was cut through the center so as to expose a square section 2" x 2". The Brinell hardness was determined at a point in the center of the square and also at one corner of the square.

The following results show the eifect of the addition of various quantities of tellurium on the hardness of the casting.

In each of the above examples, with the es-i ception of the first whichwiiiiifains. ridit'clliurium',

telluriumact equally well and reverse the graphitizing e ect of these metals.

When he teilurium is used in connection with metals such as nickel, copper, or molybdenum, greater hardness, and toughness is obtained. For example, when tellurium was added in conjunction with 2.5% of copper, the Brinell hardness was raised from 430 to 470, and when added in conjunction with 4.0% of nickel, the hardness was increased from 430 to 530.

In a similar manner, small quantities of tellurium may be introduced into those cast irons which are known as chilling irons, such as are used in the manufacture of chill rolls, chill car wheels, agricultural implements, and the like, The addition of tellurium results in an increased depth of chill and increased hardness.

For example, a light chilling iron containing 3.1% of graphite, 1.2% of silicon, .7% of manganese, .095% of sulphur, and 2% of phosphorus showed, without the addition of tellurium, a chill depth of of an inch having a Brinell hardness of 415. After adding .0025% of tellurium, the depth of chili was increased to 1 inches, and the Brinell hardness was increased to 460. After adding .005% of tellurium, the specimen was chilled through, and the Brinell hardness increased to 469. An addition of .10% of tellurium increased the Brinell hardness further to 477. It is also found that the addition of tellurium produces a sharp line of demarcation between the hard chilled outer zone and the non-chilled gray inner zone of the casting, thereby reducing the mottled zone which frequently is formed between the chilled and non-chilled zones when a chilled casting is produced in the absence of tel lurium. Further additions of tcllurium did not seem to increase the hardness further unless used in conjunction with copper, nickel, or molybdenum, or with a combination of these metals.

For the purpose of this invention, the tellurium may be alloyed with other metals, such as nickel, copper, iron, selenium, and others, depending upon the percentage of tellurium required and the degree of hardness and toughness for the particular combination of these qualities which is desired in the finished casting.

The examples given herein are to be regarded as illustrative of the manner in which the invention may be practiced, and they do not limit the scope of the appended claims.

I claim: 1 i

1. The method of producing a chilled casting having a hard chilled outer zone and a gray inner zone which comprises introducing into the molten cast iron tellurium in an amount up to 2%, and casting the iron against a metal chill "thereby increasing both the depth and the hardness of the chill over that which would be obtained in the absence of the tellurium and producing a sharp line of demarcation substantially free of mottllng between the hard chilled outer zone and non-chilled gray inner zone of the casting.

2. The method of producing a chilled casting having a hard chilled outer zone and a gray inner zone which comprises introducing into the molten cast iron a graphitizing agent, and tellurium in an amount up to 2% and effective to reverse the graphitizing effect of such agent, and casting the iron against a metal chill thereby increasing both the depth and the hardness of the chill over that which would be obtained in the absence of the tellurium and producing a sharp line of demarcation substantially free of mottling between the hard chilled outer zone and non-chilled gray inner zone of the casting.

3. The method of producing a chilled casting having a hard chilled outer zone and a gray inner zone which comprises introducing into the molten cast iron tellurium in an amount up to 2%, and an agent selected from a class consisting of copper, nickel, and molybdenum in an amount effective to induce increased hardness and toughness over that obtained by the tellurium alone, and casting the iron against a metal chill thereby increasing both the depth and the hardness of the chill over that which would be obtained in the absence of the tellurium and producing a sharp line of demarcation substantially free of mottling between the hard chilled outer zone and non-chilled gray inner zone of the casting.

4. The method of producing a chilled casting having a hard chilled outer zone and a gray inner zone which comprises introducing into the molten cast iron 9, graphitizing agent, tellurium in an amount up to 2% and effective to reverse the graphitizing effect of such agent, and an agent selected from a class consisting of copper, nickel, and molybdenum in an amount effective to induce increased hardness and toughness over that obtained by the tellurium alone, and casting the iron against a metal chill thereby increasing both the depth and the hardness of the chill over that which would be obtained in the absence of the tellurium and producing a sharp line of demar cation substantially free of mottling between the hard chilled outer zone and non-chilled gray inner zone of the casting.

5. The product produced by the claim 1.

6. The product produced by the claim 2.

7. The product produced by the claim 3.

8. The product produced by the claim 4,

9. As a new article of manufacture a car wheel produced by the method of claim 1.

method of method of method of method of OLIVER SMALLEY. 

